This research proposal aims to increase the understanding of cell division, an essential process mediated by ten essential proteins, in the bacterium Escherichia coli. In the absence of a cell division protein, the cells form long filaments with properly replicated and segregated chromosomes, but are unable to divide. An increased understanding of how E. coli divides would provide insight into the cell division process of more complex organisms, and also could lead to the development of new antibiotics targeting cell division. Co-immunoprecipitation experiments have detected a multi-protein cell division complex composed of a conserved group of proteins, FtsB, FtsL and FtsQ, which are known to interact in E. coli and in Gram-positive bacteria. Several approaches will be used to better understand the interactions and functions of components of the FtsB/FtsL/FtsQ complex. One and two hybrid methods will be used to study protein interactions in the complex, and these methods will also be used for the analysis of FtsB and FtsL mutants. The putative protein instability of FtsB and FtsL, resulting from the absence of proteins of the complex will be studied, as will the potential role of protein instability in the regulation of cell division. Finally, to gain insight into the interactions and functions of FtsB and FtsL, a mutant screen will be used to identify important residues of the two proteins that will be characterized to determine the specific cell division defect.